Central nervous system disorders affect a wide range of the population with differing severity. Generally, the major feature of this class of disorders includes the significant impairment of cognition or memory that represents a marked deterioration from a previous level of functioning.
Schizophrenia is a psychopathic disorder of unknown origin, which usually appears for the first time in early adulthood and is marked by characteristics such as, psychotic symptoms, phasic progression and development, and/or deterioration in social behavior and professional capability. Characteristic psychotic symptoms are disorders of thought content (e.g., multiple, fragmentary, incoherent, implausible or simply delusional contents, or ideas of persecution) and of mentality (e.g., loss of association, flight of imagination, incoherence up to incomprehensibility), as well as disorders of perceptibility (e.g., hallucinations), emotions (e.g., superficial or inadequate emotions), self-perceptions, intentions, impulses, and/or inter-human relationships, and psychomotoric disorders (e.g., catatonia). Other symptoms are also associated with this disorder. See, e.g., Diagnostic and Statistical Manual of Mental Disorders, 4th Ed., American Psychiatric Association (1997) (DSM-IV™).
Schizophrenia is classified into subgroups. The paranoid type is characterized by delusions and hallucinations and absence of thought disorder, disorganized behavior, and affective flattening. The disorganized type, which is also named “hebephrenic schizophrenia,” in which thought disorder and flat affect are present together. The cataconic type, in which prominent psychomotor disturbances are evident, and symptoms may include catatonic stupor and waxy flexibility. The undifferentiated type in which psychotic symptoms are present but the criteria for paranoid, disorganized, or catatonic types have not been met. The symptoms of schizophrenia normally manifest themselves in three broad categories, i.e., positive, negative and cognitive symptoms. Positive symptoms are those, which represent an “excess” of normal experiences, such as hallucinations and delusions. Negative symptoms are those where the patient suffers from a lack of normal experiences, such as anhedonia and lack of social interaction. The cognitive symptoms relate to cognitive impairment in schizophrenics, such as lack of sustained attention and deficits in decision making. The current antipsychotics may be successful in treating the positive symptoms but fare less well for the negative and cognitive symptoms.
Cognitive impairment includes a decline in cognitive functions or cognitive domains, e.g., working memory, attention and vigilance, verbal learning and memory, visual learning and memory, reasoning and problem solving (e.g., executive function, speed of processing and/or social cognition). In particular, cognitive impairment may indicate deficits in attention, disorganized thinking, slow thinking, difficulty in understanding, poor concentration, impairment of problem solving, poor memory, difficulties in expressing thoughts, and/or difficulties in integrating thoughts, feelings and behavior, or difficulties in extinction of irrelevant thoughts.
Agitation is a well-recognized behavioral disorder with a range of symptoms, including hostility, extreme excitement, poor impulse control, tension and/or uncooperativeness. Agitation is common in the elderly and often associated with dementia such as those caused by Alzheimer's disease, Parkinson's disease, and Huntington's disease, and by diseases that affect blood vessels, such as stroke or multi-infarct dementia, which is caused by multiple strokes in the brain. An estimated five percent of people aged 65 and older and up to 20 percent of those aged 80 and older are affected by dementia; of these sufferers, nearly half exhibit behavioral disturbances, such as agitation, wandering, and violent outbursts. Agitated behaviors can also be manifested in cognitively intact elderly people and by those with psychiatric disorders other than dementia.
Dementia is characterized by several cognitive impairments including significant memory deficit and can stand alone, or be an underlying characteristic feature of a variety of diseases, including but not limited to, Alzheimer's disease, Parkinson's disease, Huntington's disease, and multiple sclerosis.
Therefore, there is a great need for effective treatments of various neurological disorders, including but not limited to, psychosis and schizophrenia.